The control of gene expression by neurotransmitters and neuropeptides begins with the binding of ligands to specific membrane receptors. Receptor activation causes changes in cell function by generating a variety of second messengers, including cyclic nucleotides and divalent cations. These processes modulate gene expression by changing the properties of specific transcription factors that recognize discrete sequences in gene promoters. The overall goal of this Program is to determine how receptor-activated second messenger systems produce changes in gene expression. The first goal is to determine whether intracellular targeting of protein kinase A (PKA) determines the specificity of cAMP actions. Activation of PKA is the major pathway for effecting changes in cellular function in response to increases in cAMP. Dr. Scott (Project 2) has proposed that PKA localization is determined through interactions between the regulatory subunit, RII, and a family of anchoring proteins known as AKAPs. Having identified AKAPs that are specific for distinct subcellular locations, he is now in a position to definitively test the functional importance of 'targeting' in PKA- mediated cellular events. His studies will address both cytoplasmic (collaboration with Dr. Maurer, Project 4) and nuclear (collaboration with Drs. Goodman and Soderling, Projects 1 and 3) actions of PKA. The second goal is to determine how calcium ion alters gene expression through activation of calcium/calmodulin (CAM)-dependent protein kinases and phosphatases. Dr. Soderling (Project 3) and Dr. Maurer (Project 4) have determined that the transcription factor CREB is activated by CAM kinase II. The activation of CAM kinase IV is not straightfoward, however, as another kinase (CAM kinase kinase) is required for maximal CREB phosphorylation. A collaborative effort involving Projects 1, 3, and 4 will elucidate the pathway of calcium- regulated gene activation through CREB and other transcription factors. Many of the projects in this program utilize the phosphorylation of CREB as a model for second messenger-regulated gene activation. Clearly, other transcription factors can also transduce second messenger-mediated signal, as well. The third goal is to determine whether CBP, a co-activator for CREB and possibly other transcription factors, contributes to transcriptional 'signal integration'. Studies in Project 1 take advantage of the genetics of Drosophila to determine whether CBP serves as a transcriptional 'integrator'. A collaboration between Dr. Goodman (Project 1) and Dr. Maurer (Project 4) uses a reconstituted chromatin system derived from Drosophila extracts to elucidate the mechanism of CBP-mediated gene activation.